The present invention relates to a method for producing an electronic signature which incorporates all of the visual aspects of a true manual signature and, more specifically, to a method for producing a true-life electronic signature which is both secure and authenticatable.
Electronic documents are rapidly replacing paper documents as the preferred means of communicating information. For example, inter-office memos are now frequently distributed via e-mail rather than as a paper document. As office workers and other computer users have become more comfortable with reading and manipulating such electronic documents, the frequency with which paper documents are being replaced has increased. Electronic documents offer many advantages over paper documents. For example, electronic documents are easier to store. The same electronic document can easily be sent to multiple recipients, without tedious reproduction of the document with a photocopying machine, for example. Thus, many computer users now prefer electronic documents over paper documents for communication.
One difficulty with electronic documents has been the need for authentication and verification of the author of the document. Paper documents are typically signed or initialed by the author of the document with a pen, so that the paper material itself is indelibly marked. Later attempts to remove or alter the signature from the paper document are thus clearly visible, so that the authenticity of the signature is easy to determine from an inspection of the document itself.
Such authenticity is particularly important for legal documents, such as contracts, and for financial documents, such as checks. Such documents do not simply provide information. Instead, they authorize the performance of a specific act, such as transferring money from the bank account of the signator of the check. Thus, these types of documents require particularly stringent standards for authentication and verification, in order to prevent acceptance of a forged signature.
Until recently, no equivalent to the manual signature was available for electronic documents, let alone an equivalent which would satisfy the stringent standards for legal and financial documents. Simply capturing a manual signature electronically, and then pasting the electronic signature into the document, does not provide any authentication or verification. Such a simple electronic signature can be easily copied without the knowledge or authorization of the author, in a manner which is not detectable as a forgery. Thus, simple electronic signatures do not provide a satisfactory equivalent to the manual signature.
A method for providing a verifiable electronic signature was disclosed in U.S. Pat. No. 5,606,609. This method includes embedding a xe2x80x9csecurity objectxe2x80x9d in an electronic document. The security object can then be verified at a later date to authenticate the author of the document, for example. The security object was described as an xe2x80x9celectronic chopxe2x80x9d, which could be a digitized rendering of the author""s signature, or some other image. However, no method is described for producing such a digitized rendering for the signature. Merely using an electronic scanner to capture an image such as a manual signature is not satisfactory because of the low quality and resolution of the captured image. The captured image should have a typographical quality at least as good as the rest of the electronic document. Furthermore, if an electronic signature is to be accepted as the equivalent of a manual signature, it must look like a true-life handwritten signature, regardless of the quality of the scanning device. Thus, the electronic signature produced according to the method disclosed in U.S. Pat. No. 5,606,609 lacks these important characteristics.
There is therefore a need for, and it would be useful to have, a method for producing an electronic signature which is both verifiable and which closely resembles its manual, handwritten counterpart, with high quality resolution and visual appeal.
According to the present invention, there is provided a method for producing an electronic signature in a font format from a manual signature, comprising the steps of: (a) providing a raster image of the manual signature; (b) cleaning the raster image to remove noise, such that the raster image is a cleaned image; (c) locating a plurality of edges of the cleaned image; (d) producing an outline of the cleaned image from the plurality of edges; (e) analyzing the outline to determine a plurality of guidelines for the cleaned image; and (f) hinting the cleaned image from the plurality of guidelines to produce the electronic signature in the font format. Preferably, the raster image is in a format selected from the group consisting of a bitmap image and a graphic software application image. Also preferably, the noise includes pixels selected from the group consisting of solitary black pixels and missing pixels.
Preferably, the edges are located by finding a plurality of feature points of the cleaned image, the feature points being selected from the group consisting of curve points, horizontal extremum, vertical extremum, corners and tangents. More preferably, the outline includes at least one closed sequence of Bezier curves and straight line segments connected end-to-end. Most preferably, the guidelines are determined according to the horizontal extremum points, and the vertical extremum points.
Preferably, the font format is a TrueType(trademark) font. More preferably, the step of hinting the image includes identifying at least one hint selected from the group consisting of stems and overshoot controls.
According to a preferred embodiment of the present invention, the method further comprises the step of: (g) preparing a digital chop object from the electronic signature in the font format by adding a rasterizer for the font format, the rasterizer being capable of rendering the electronic signature such that the electronic signature is converted into a visible image. Preferably, the digital chop object is an OLE(trademark) software object. More preferably, the digital chop object further includes a safeguard mechanism such that the digital chop object is operable substantially only if a password is entered.